In recent years, semiconductor integrated circuits, information storage media such as hard disks, micromachines, and the like have been processed in highly fine patterns. In the fields of processing such workpieces, attention has been attracted to the use of an energetic beam such as a high-density ion beam which is highly linear, i.e., highly directional, and has a relatively large beam diameter. For example, the energetic beam is applied to a workpiece for depositing a film thereon or etching the workpiece.
As beam sources of such energetic beams, there have been used beam generators which generate various kinds of beams including a positive ion beam, a negative ion beam, and a radical beam. The positive ion beam, the negative ion beam, or the radical beam is applied to a desired area of a workpiece from the beam source, for thereby locally depositing a film on the workpiece, etching the workpiece, modifying the surface of the workpiece, or joining or bonding parts of the workpiece.
In the case of a beam source which applies charged particles such as positive ions or negative ions to a workpiece, an insulated workpiece cannot be processed because of a charge build-up phenomenon in which electric charges are built up on the workpiece. Further, since the ion beam emitted from the beam source tends to spread due to the space-charge effect, the workpiece cannot be processed in a fine pattern.
In order to solve the above problems, there has been proposed a method of introducing electrons into the ion beam to neutralize the electric charges. This method can balance the electric charges on the workpiece on the whole. However, since local unbalance of the electric charges still remains on the workpiece, the workpiece cannot be processed in a fine pattern.
In the case where ions are extracted from a plasma source and applied to a workpiece, if a radiation (e.g., an ultraviolet ray) produced by the plasma source is applied to the workpiece, then the radiation adversely affects the workpiece. Thus, it is necessary to shield the workpiece from an adverse radiation (e.g., an ultraviolet ray) emitted from the plasma source.